castling in check

is it allowed to castle when you're king is in a otherwise checked
position(ie if you don't castle you lose)

You cannot castle when your king is in check, or when it would move
into a square where it would be in check. You can castle if your rook is
attacked or would be on the squares where it moves (for O-O-O
castling).

Rein

You are also not permitted to castle through check. Imagine your
king must traverse every square on the way to its eventual location; if
your king would be in check were he to stop on that square, then he
cannot castle through that square.

You're absolutely right! Rereading my post, I realize that I didn't
indicate that, even though I *thought* I had... LOL! I should have
said... "Move your king into -- OR THROUGH -- a square where it
would be in check." When I was younger I always used to picture
somwthing like a king moving from one side of his caste bedroom to
the other... if he moves past a window, he can still be shot by the
archer / bishop! Hey, I was young, what do you expect? ;-)

Thanks for mentioning it! How about another game, sir? :-D
Rein

Sure Rein, I'll send one right over.

I understand the bit about the king not moving through/into/out of
check. What about the rook. Can you castle if it is attacked, or if it
has to move through a checked space?
(or would that mean that you king would be too??? Help, it's Friday,
my brain's fried)

You can castle even if the rook is under attack. When castling to the queenside, the rook 'moves through' b1 (b8). The kings 'only' goes to c1 (c8) so if b1 is under attack, the rook passes a checked space, but the king doesn't. Friday.